Even though walking is low impact (walkers hit the ground with less than half the force that runners do), your feet are still pounding the pavement. In one mile, a 150-pound woman puts the equivalent of 127,000 pounds of accumulated force on each foot, according to Marlene Reid, a podiatrist in Chicago and a spokesperson for the American Podiatric Medical Association. Fitness walking in the wrong shoes can slow you down, and it can also lead to joint problems, blisters, and shin pain.

Walkers often make the mistake of using running shoes. But walkers' feet, unlike runners', need a lower, more rounded heel to help them ease into each stride, and a flexible forefoot to help the push-off.